Thallium bromide (TlBr) is a wide bandgap, high-atomic number semiconductor, giving it certain desirable properties for use in gamma ray detection and spectroscopy. For example, as compared with commercially available cadmium zinc telluride (CZT), TlBr has higher atomic number that yields a higher photoelectric absorption, and wider bandgap that potentially yields lower dark current, enabling low-noise detectors with greater thickness than may be realized in CZT.
Conventional gamma ray detectors and other devices incorporating TlBr semiconductor elements have faced limited usefulness as a result of aging processes that generally cause TlBr-based detectors to become inoperable after less than 6 months of continuous use at room temperature. Improvements in purity of TlBr materials used in gamma ray detectors have shown gains in detector efficiency, but have not yielded significant improvement in rates of aging of TlBr-based devices. Material polarization and contact-metal corrosion in TlBr-based devices have been believed to be caused by migration of vacancies in TlBr crystals, causing charge imbalances that result in polarization of the crystals themselves or chemical reactions between crystal ions and electrical contacts on the crystal that cause corrosion of the contacts.